PhpUnit and Phalcon Models

Hello to everyone, i just started to work with phalcon this weekend.
I wanted to set a simple Authentication Script. I started to create some Models and there relations. After that worked, i startet to write tests for it.

worked in almost all cases but in some cases it didn´t and i received again the message
"Service 'db' wasn't found in the dependency injection container".
That happens when i am for e.g calling findFirst. the find() function is working fine but not findFirst()

So i have it now in the bootstrap and in the unitTestCase file. When i am deleting the code out of one, then it is not working anymore. I think i have a major issue with the Test setup because of the tearDown with DI.

Also when i am just creating a second Test file now with a simple equal test 0=0, the whole first file with the Models is not working anymore and i get the message:

Phalcon\Mvc\Model\Exception : A dependency injector container is required to obtain the services related to the ORM